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From:   Javier Gonzalez <javier@cnexlabs.com>
To:     =?utf-8?B?TWF0aWFzIEJqw7hybGluZw==?= <mb@lightnvm.io>
CC:     "Konopko, Igor J" <igor.j.konopko@intel.com>,
        Marcin Dziegielewski <marcin.dziegielewski@intel.com>,
        Hans Holmberg <hans.holmberg@cnexlabs.com>,
        Heiner Litz <hlitz@ucsc.edu>,
        Young Tack Tack Jin <youngtack.jin@circuitblvd.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lightnvm: limit get chunk meta request size
Thread-Topic: [PATCH] lightnvm: limit get chunk meta request size
Thread-Index: AQHUEdsSzTW28Ywxt0+HVRJbpGneyqR931SA
Date:   Tue, 3 Jul 2018 19:10:41 +0000
Message-ID: <C0B26672-CFD1-4058-A979-48341CD40F8D@cnexlabs.com>
References: <20180702080223.13214-1-mb@lightnvm.io>
In-Reply-To: <20180702080223.13214-1-mb@lightnvm.io>
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> On 2 Jul 2018, at 10.02, Matias Bj=C3=B8rling <mb@lightnvm.io> wrote:
>=20
> For devices that does not specify a limit on its transfer size, the
> get_chk_meta command may send down a single I/O retrieving the full
> chunk metadata table. Resulting in large 2-4MB I/O requests. Instead,
> split up the I/Os to a maximum of 256KB and issue them separately to
> reduce memory requirements.
>=20
> Signed-off-by: Matias Bj=C3=B8rling <mb@lightnvm.io>
> ---
> drivers/nvme/host/lightnvm.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/nvme/host/lightnvm.c =
b/drivers/nvme/host/lightnvm.c
> index b9989717418d..3b644b0e9713 100644
> --- a/drivers/nvme/host/lightnvm.c
> +++ b/drivers/nvme/host/lightnvm.c
> @@ -583,7 +583,13 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev =
*ndev,
> 	struct ppa_addr ppa;
> 	size_t left =3D nchks * sizeof(struct nvme_nvm_chk_meta);
> 	size_t log_pos, offset, len;
> -	int ret, i;
> +	int ret, i, max_len;
> +
> +	/*
> +	 * limit requests to maximum 256K to avoid issuing arbitrary =
large
> +	 * requests when the device does not specific a maximum transfer =
size.
> +	 */
> +	max_len =3D min_t(unsigned int, ctrl->max_hw_sectors << 9, 256 * =
1024);
>=20
> 	/* Normalize lba address space to obtain log offset */
> 	ppa.ppa =3D slba;
> @@ -596,7 +602,7 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev =
*ndev,
> 	offset =3D log_pos * sizeof(struct nvme_nvm_chk_meta);
>=20
> 	while (left) {
> -		len =3D min_t(unsigned int, left, ctrl->max_hw_sectors =
<< 9);
> +		len =3D min_t(unsigned int, left, max_len);
>=20
> 		ret =3D nvme_get_log_ext(ctrl, ns, =
NVME_NVM_LOG_REPORT_CHUNK,
> 				dev_meta, len, offset);
> --
> 2.11.0

Is this a v2? I remember seeing this patch being posted before [1]. It
still looks good to me :)


[1] https://lkml.org/lkml/2018/6/12/466


Reviewed-by: Javier Gonz=C3=A1lez <javier@cnexlabs.com>


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